Process of refrigeration using mixture sf6 and chcif2

ABSTRACT

MONOCHLORODIFLUOROMETHANE (CHC1F2) AND SULFUR HEXAFLUORIDE (SF6), IN CERTAIN PROPORTIONS, FORM MIXTURES HAVING UNUSUALLY HIGH REFRIGERATION CAPACITY AND WHICH ARE THEREFORE ESPECIALLY ADAPTED FOR USE AS REFRIGERANTS IN HIGH CAPACITY, LOW TEMPERATURE REFRIGERATION SYSTEMS.

U.S. Cl. 252-67 United States Patent PROCESS OF REFRIGERATION USING MIXTURE SF AND CHCIF Kevin P. Murphy, Bernardsville, and Richard F. Stahl,

Madison, N.J., assignors to Allied Chemical Corporation, New York, N.Y.

No Drawing. Filed Nov. 21, 1968, Ser. No. 777,897 Int. Cl. C09k 3/02 4 Claims ABSTRACT OF THE DISCLOSURE Monochlorodifluoromethane (CHClF and sulfur hexafiuoride (SF in certain proportions, form mixtures having unusually high refrigeration capacity and which are therefore especially adapted for use as refrigerants in high capacity, low temperature refrigeration systems.

BACKGROUND OF THE INVENTION Sulfur hexafiuoride (SP is a known refrigerant (US. Pat. 1,778,033). The lower aliphatic hydrocarbons, when substituted by fluorine and chlorine, are well known to have potential as refrigerants (US. Pat. 1,968,049). Many of these halocarbon materials exhibit certain desired properties for refrigeration purposes including low cost, low specific volume, low toxicity and non-flammability, which characteristics have resulted in the extensive use of such compounds in a large number of refrigeration applications. Examples of such compounds include dichlorodifluoromethane (CCI F B.P. 21.6 F.; chlorodifluoromethane (CHCIF B.P. -41.4 F.; fluorodichloromethane (CHC-l F), B.P. 48.1 F.; fluorotrich'loromethane (CCl F), B.P. 78.4 F., tetrafluorodichloroethane (CClF COlF B.P. 38.4 F. and trifluoromethane (CHF B.P.1l9.9 F.

While these chloro-fluoro derivatives provide an ade quate range of refrigerants for many purposes, only a very few exhibit sufiiciently high refrigeration capacities to offer any significant potential as low temperature refrigerants. A large number of refrigerants of different capacities are required to permit flexibility of design and the art is continually faced with the problem of providing new refrigerants as the need arises for new capacities and types of installations.

It is Well known that refrigeration capacity is largely a function of the vapor pressure of the refrigerant at the evaporating temperature. Accordingly, it would be logical in seeking refrigerants possessing higher capacities to study those exhibiting higher vapor pressures. The use of higher pressure refrigerants, however, requires the use of heavier and more costly equipment components to maintain the desired safety margins. Any refrigerant composition which could produce an increase in capacity without a corresponding increase in operating pressures, while possessing other desirable refrigeration properties, would be highly valuable to the industry.

An object of this invention is to provide a novel range of refrigerant mixtures which possess significantly higher capacity levels than SF but which can be used in refrigeration systems with lower or no significantly higher operating pressures than would be required for SP alone.

It is another object of the present invention to provide new compositions especially suitable for use as low temperature refrigerants.

Another object of the invention is to provide non-flammable, low boiling refrigerant compositions having high refrigeration capacities.

Other objects and advantages of the invention will become apparent from the following description.

SUMMARY OF THE INVENTION In accordance with the invention, it has been discovered that mixtures consisting of monochlorodifluoromethane (CHClF B.P. 41.4 F.) and sulfur hexafluoride (SP B.P. -5 8 F.) containing about 35-92 mol percent SP although possessing vapor pressures intermediate the vapor pressures of the individual components depending on concentration, as would be expected; said mixtures possess refrigeration capacities which are significantly higher than the refrigeration capacities of either of the CHClF or SP components alone. This latter property is highly unexpected, particularly when considered in the light of the vapor pressure characteristics of these mixtures. The phenomenon which results in the unusually high refrigerating capacities is not understood.

Mixtures as defined above in which the SP component is present in a molar percentage between about 40-60 are preferred, since such mixtures possess freezing points below about C., which is preferred for some refrigeration applications. Still preferred are mixtures as defined above in which the molar percentage of SE; is between about 48-52. A preferred mixture is one in which the molar percentage of SE; is about 50.

A further unexpected property of the mixtures falling within the scope of the invention is that the compression ratios of said mixtures are lower than those of the individual mixture components alone. This has practical significance in terms of higher volumetric efiiciency of the compressor and longer compressor life.

The mixture of the invention may be employed to produce refrigeration in a conventional manner by condensing the mixtures and thereafter evaporating said mixtures in the vicinity of a body to be cooled.

The mixtures of the invention may also be employed for other applications such as for aerosol propellants, power cycle fluids, gaseous dielectrics, heat transfer media and low temperature solvents.

EXAMPLE 50 mol percent mol percent Evaporator pressure (p.s.i.a.) 19.1 60. 2 55. 4 Condenser pressure (p.s.i.a.) 173 385 338 Compression ratio 9. 05 6. 40 6. 10 Capacity (cu. it./min per ton)- 8.28 4. 4 3. 10 Relative capacity 100 188 267 The above data show that the 50 mol percent CHClF 50 mol percent SF mixture has 267% of the capacity of CHCIF alone. The 50 mol percent CHCIF /SO mol percent SP mixture has 142% of the capacity of SE; alone. These figures are particularly surprising when it is observed, as shown by the above data, that the operating pressures during use of the CHCIF /SF mixture are intermediate the operating pressures when either CHClF or SF are used alone.

As can further be seen from the above data, the subject mixture also exhibits a lower compression ratio than either of the mixture components.

Mixtures of CHClF and SF in accordance with the invention in which the SP concentration varies over the entire range of about 35-92 mol percent, all exhibit higher refrigeration'capacities and lower compression ratios than either of the components.

3 I 4 We claim: References Cited 1. The process of producing refrigeration which corn- UNITED STATES PATENTS rises condensin a mixture consisting essentially of HC1F and SF in which the mol percent of SP is in 2641579 7/1953 Benmng 252-67 the range of about 35-92 and thereafter evaporating said 5 OTHER REFERENCES mixture in the vicinity of the y to be Cooled- Chemical Abstracts, vol. 54, co]. 4601g; vol. 61, col.

2. The process according to claim 1 in which the mix- 13892b. ture contains about 40-60 mol percent of SF 3. The process according to claim 1 in Which the mol JOHN WELSH Pnmary Exammer percent of SP is in the range of about 4852. 10 U S Cl XR 4. The process according to claim 1 in which the mol percent of SE; is about 50. 62-114; 252--30 S 

